Abstract 19164: Products of Murine Cytochrome P450 Cyp2j Locus Regulate Pulmonary Vascular Response to Alveolar Hypoxia

Epoxyeicosatrienoic acids (EETs) are eicosanoids with potent vasoactive effects. Multiple cytochrome P450 enzymes, including CYP2J2, synthesize EETs in humans. However, genetic analysis of the contributions of CYP2J2 to physiologic processes in humans has been confounded by the allelic expansion in rodents: mice have 8 Cyp2j genes that encode epoxygenases similar to CYP2J2. To investigate the role of CYP2J2, we created mice bearing a 626 kb deletion spanning the murine Cyp2j locus using a combination of homologous and site-directed recombination strategies. Two bacterial artificial chromosomes (BACs) covering the 2 ends of murine Cyp2j locus were modified to allow an integrase-mediated site-specific recombination event to fuse the BACs and form a deletion replica that could be propagated in E. coli. The replica was introduced into mouse ES cells to ultimately enable generation of Cyp2j-null mice (Cyp2j-/-). RT-MLPA (Multiplex Ligation-independent Probe Amplification) revealed that the 8 Cyp2j genes were expressed in wild-type (WT) but not in Cyp2j-/- mice. A mouse strain in which the Cyp2j locus deletion was complemented by transgenic delivery of BAC sequences encoding human CYP2J2 was also created (Cyp2j-/-tg). Systemic and pulmonary hemodynamic parameters did not differ in anesthetized WT, Cyp2j-/-, and Cyp2j-/-tg mice at baseline. Hypoxic pulmonary vasoconstriction (HPV) was monitored by measuring left pulmonary vascular resistance (LPVR) and systemic arterial oxygenation (PaO2) before and during left main stem bronchial occlusion (LMBO). LMBO did not alter systemic arterial pressure in any genotype. LMBO increased LPVR 2.0- and 2.3-fold in WT and Cyp2j-/-tg mice, respectively, due to HPV (P<0.05 for both). LMBO did not change LPVR in Cyp2j-/- mice. During LMBO, PaO2 was greater in WT and Cyp2j-/-tg mice than in Cyp2j-/- mice (P<0.05 for both) demonstrating that Cyp2j deficiency impairs matching of ventilation with perfusion (V/Q). Administration of MS-PPOH, a selective inhibitor of CYP450 epoxygenase, to WT mice also blocked the ability of LMBO to increase LPVR. These data suggest that products of Cyp2j epoxygenase activity contribute to the pulmonary vasoconstriction produced by alveolar hypoxia and preservation of V/Q matching.